Use of anomalous small-angle X-ray scattering for the investigation of highly charged colloids

Abstract

We present a study of the radial structure of a spherical polyelectrolyte brushes by anomalous small-angle X-ray scattering. The spherical polyelectrolyte brushes consist of a solid poly(styrene) core of ca. 100 nm diameter onto which long linear chains of poly(acrylic acid) (PAA) are densely grafted. A sufficiently high pH, these polyelectrolyte chains are fully charged. Rubidium ions are used as counterions because their adsorption edge (15 199.6 eV) can be conventiently reached by synchrotron radiation. By performing small-angle X-ray scattering studies at different energies of the incident radiation, the contribution of the Rb + counterions can be analyzed separately. The scattering contribution of the counterions can be derived and compared to the scattering intensity of the entire particle. The distributions of the macro-ion and of the counterions are shown to be very similiar. This shows that the counterions must be confined within the brush.

Structure analysis of multiphase systems by anomalous small-angle X-ray scattering

“…Three scattering functions, resonant, nonresonant (or off-resonant) and a cross-term, are determined from at least three scattering curves at each available absorption edge. The resonant function originates from the spatial arrangement of the resonant atoms only, while the non-resonant is thought to be the scattering one could obtain by scattering of X-rays with energy far from any absorption edge [10,18]. Similar equations were reported also by Epperson and Thiyagarajan [37].…”

“…Equations connecting the volume fractions can be obtained by using the partial invariants, ij Q . Using (18) and (38), we obtain relations similar to (39)…”

“…Thus, it is used mainly to study solid matter; alloys [1][2][3][4][5][6][7][8][9], glasses [10,11], metal catalysts [12][13][14] and polymer composites [15,16]. ASAXS investigations of charged colloids [17][18][19] and soft mater objects [20] were also published. ASAXS has been done even at the S, P and…”

Extracting water and ion distributions from solution x-ray scattering experiments

“…13,18 Efforts to extract the contribution from ions to ASAXS profiles date back to 2003 with the work of Ballauff and coworkers. 15,19 Using multiple energy ASAXS, they were able to decompose the total scattering intensity into solute-ion and ion-ion contributions, though limited to spherical solutes. Recently, Meisburger et al proposed a similar approach to a) Author to whom correspondence should be addressed.…”

Anomalous small-angle X-ray scattering from charged soft matter

“…The Eq. (4) contains three additive components: F 2 0 (q), the energy independent normal SAXS, F 0 (q)v(q), the cross-term involving the amplitudes of normal SAXS and the resonant scattering of the anomalous atoms, and v 2 (q), the weak resonant scattering term (self-term) originating from the anomalous atoms [5,12]. Having measured I(q) at least at three energies, a decomposition of the scattered intensity into the three partial intensities in Eq.…”